Temperature measures the average random kinetic energy of a system's particles, whereas internal energy is the total random kinetic energy and intermolecular potential energy of all its particles. Therefore, two systems can have the same temperature but different internal energies.
This is part of B.1 Thermal energy transfers and applies to both SL and HL.
| Temperature | Internal energy |
|---|---|
| Relates to the average random kinetic energy per particle | Includes the total random kinetic energy of all particles plus their total intermolecular potential energy |
| An intensive property, so it does not depend directly on the amount of substance | An extensive property, so it generally increases when the amount of substance increases |
| Measured in kelvin, K, or degrees Celsius, °C | Measured in joules, J |
| Determines the direction of resultant thermal energy transfer | Changes when energy is transferred by heating or work |
For an ideal monatomic gas, the average translational kinetic energy per molecule is